Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Biological soil crusts in Alberta’s grasslands : increasing our knowledge of their taxonomy, diversity, and sensitivity to drought and defoliation

Auteur : Lewis, Megan C

Université de soutenance : University of Alberta

Grade : Master of Science (MS) 2022

Résumé partiel
Biological soil crusts (BSCs) play a central role in the biodiversity, health, resilience, and function of drylands like Alberta’s grasslands. In Alberta, much of the biocrust cover consists of lichens, and many crusts are dominated by species of Cladonia. Despite the drought-resistant nature of biocrusts, they have been found to be sensitive to changes in precipitation and disturbance in other regions. This finding leads to questions of if, and how, land-management strategies should change to retain rangeland function as drought becomes more frequent. To answer these questions we need monitoring and experiments investigating biocrust response to change. However, for a group of lichens in Alberta’s grassland biocrusts, the Cladonia cariosa group, taxonomic boundaries are imprecise, potentially obscuring changes in biocrust communities. To clarify boundaries in the Cladonia cariosa group, I implemented an integrative taxonomic study using morphology, secondary chemistry, a multi-locus molecular dataset, and a genotype-by-sequencing (GBS) dataset. While the multi-locus study using the internal transcribed spacer region of nuclear rDNA (ITS) and DNA-dependent RNA polymerase 2 (rpb2) provided low resolution, the GBS dataset generated a highly-supported phylogeny. Three lineages corresponded to previously described species in the group, Cladonia cariosa, Cladonia symphycarpa, and Cladonia acuminata, and two lineages correspond to undescribed species. While Cladonia cariosa, Cladonia symphycarpa, and Cladonia acuminata could clearly be differentiated by morphology and chemistry, the two undescribed species had few distinguishing traits from Cladonia symphycarpa, and are thought to be semi-cryptic.

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